The construction of pneumatic rubber tires by conventional methods, comprising the assembly of components such as carcass plies, beads and thread, led to an undesirable number of sub-standard tires because of misalignment of parts and because of non-uniformities such as splices. Conventional assembly methods are also costly because of the many manual operations involved. Consequently, the manufacture of hollow tires and hollow wheels from synthetic resins or thermoplastic polymers by stationary or rotational molding techniques have been developed, British Pat. No. 1,033,377, U.S. Pat. No. 3,208,500 and U.S. Pat. No. 3,470,933. Hollow tires manufactured by molding resins or thermoplastics reduce both the occurrence of non-uniformities and the number of manual steps but they must be mounted on a separate rim and consequently have the attendant slipping and balancing problems associated with tire-rim assemblies. Hollow wheel manufactured by molding resins or thermoplastics, in addition to reducing non-uniformities and manual operations, eliminate the need for a rim; however, because of expansive sidefaces, they cannot withstand substantial pneumatic pressure without ballooning and are limited in their load-bearing capacity.
An integral tire and wheel formed as a unit by molding techniques is also known. For example, Keefe, U.S. Pat. No. 3,062,254, describes a molded tire and wheel in which the wheel is internally supported by a radial web. An integral tire and wheel comprising a tire body reinforced by textiles and a wheel having an integral peripheral rim in which the wheel and rim are stiffened by a resin material which material may be further reinforced by fiber, preferably fabric, is disclosed by McHugh, U.S. Pat. No. 3,362,451. However, the disclosure suggests that the integral tire and wheel of the patent having no additional support in the wheel portion may exhibit excessive lateral deflections during use since the preferred construction provides for reinforcing the walls of the wheel portion by a pair of annular metallic plates, col. 4, lines 10-24. In both patents, assembly of the integral tire and wheel requires placing separate parts in the mold (in one case, a web and in the other case, a fabric ply) which placements afford opportunity for misalignments to occur.
This invention provides an integral pneumatic tire and wheel free of discrete reinforcing elements which integral tire and wheel may be formed by molding techniques from moldable material which may be the same material in both the tire portion and wheel portion. The integral tire and wheel of the invention possesses several advantages. One advantage, because it has no metal rim, is its light weight which leads to fuel savings. Another advantage due to its improved uniformity is that it requires no balancing which improvement in part is due to the absence of separate components which may misalign and because the tire and wheel may be molded entirely from homogeneous material. Still another advantage is that the construction of the integral tire and wheel requires fewer operations resulting in reduced cost. Also, the wheel portion is free of separate supporting means yet exhibits adequate lateral stability. Moreover, when the tire and wheel is made from select materials, it is capable of high speed operation with loads typical for motor vehicles. These and other advantages will become apparent as the description of the invention proceeds.